Contact lenses are widely used for correcting many different types of vision deficiencies. These include defects such as near-sightedness and far-sightedness (myopia and hypermetropia, respectively), astigmatism vision errors, and defects in near range vision usually associated with aging (presbyopia). Current opinion holds that presbyopia occurs as a person ages when the lens of eye begins to crystallize and lose its elasticity, eventually resulting in the eye losing the ability to focus on nearby objects.
Some presbyopic persons have both near-vision and far-vision defects, requiring bifocal lenses to properly correct their vision. Many people prefer wearing contact lenses to correct their vision rather than bifocal eyeglasses. However, creating a bifocal or simultaneous vision lens for presbyopes entails finding “compromise” vision, i.e., vision that is acceptable in both near and far vision, but perfect in neither.
Testing refractive errors of the eye involves several tests, some of which are subjective, and others that are objective in nature. Objective refraction tests include the use of retinoscopy, phoropter systems, wavefront sensors, and autorefractors. A phoropter can be manipulated by a control unit so that an operator's movement can be minimized during the testing procedure (see U.S. Pat. No. 4,861,156, which is expressly incorporated by reference as if fully set forth herein).
Refractive errors in the eye may also be detected by using wavefront sensors, such as for example a Shack-Hartmann wavefront sensor. Measurements of the wavefront aberrations of the eye, to a high degree of precision, using an improved Hartmann-Shack wavefront sensor are described in U.S. Pat. No. 5,777,719, which is expressly incorporated by reference as if fully set forth herein. The wavefront sensor illuminates the retina with a narrow cone of light from an LED or laser. The refractive errors of the eyes are measured and computed as a power map or wavefront representation such as a basis set of the Zernike polynomials. Starting at the retina, an ideal wavefront is generated which passes through the optical path of the eye. As the wavefront exits the eye, it contains a complete map of the eye's aberrations for analysis by the sensor. Once the wavefront is received by the sensor, a complex series of analyses are performed to provide a “complete” picture of the eye's optical path.
Objective refraction tests often to not correlate with subjective sphero-cylindrical correction or presbyopic correction. Because vision is subjective, differences in an eye's aberration, the individual's neural processing, and the individual's visual requirements may limit the effectiveness of objective tests. Subjective eye tests are more interactive than objective tests and may provide better compensation for an eye's aberration, the individual's neural processing, and the individual's visual requirements. Subjective tests can be performed by using adaptive optic phoropters, for example. These are new devices that recently became commercially available.
In addition, even if the technology were currently available to accurately determine an ideal vision correction on a customized basis, the technology is not currently available to fabricate, in a practical way, an ophthalmic lens having a refractive surface with the correction that is stable and registered to an eye's line of sight.
Thus it can be seen that needs exist for improvements to ophthalmic methods and systems to optimally correct for aberrations in the eye and to fabricate complex lenses with the needed corrections to provide optimal vision. It is to such improvements that the present invention is primarily directed.